During the brewing process, wort is heated up and boiled after the lautering process for increasing the concentration of the wort in a desired manner by evaporating superfluous water. Moreover, enzymes are destroyed in this process and the wort is made sterile. This heating process can, for instance, be carried out in a so-called wort kettle. While wort is being boiled in the wort kettle, hop is added to the wort in a desired concentration and at a predetermined time, with the hop releasing its bitter substances to the wort. After completion of this process the wort is pumped for further processing purposes with the aid of a wort casting pump, for instance, into a whirlpool tank in which the hot break is deposited.
The processes which are carried out in the wort kettle, i.e., mainly the heating, boiling and hopping of wort, as well as the processes which are carried out in the whirlpool tank, can also be performed in a combined wort kettle and whirlpool apparatus. After the hot break has been separated, the clear wort is pumped out from this combined tank with the aid of a wort casting pump for further processing.
To avoid idle times which occur before the wort is introduced into the wort kettle or into the combined vessel, one or a plurality of pre-run vessels are often used in cases where a large number of brews are to take place in succession on a single day. A boiling device which serves to heat the wort is here positioned within such a pre-run vessel. After the wort has been heated up in a pre-run vessel, it is pumped into the wort kettle or into the combined wort kettle and whirlpool apparatus with the aid of a casting pump.
So-called inner boilers, specifically inner tube-type boilers, are often used for heating up the wort in such vessels. Such an inner tube-type boiler is described in patent specification DE 43 04 383 C1 for use in a wort kettle. The inner boiler is centrally supported on the bottom of the wort kettle, for instance, on supports. The wort can then pass under the boiler and is driven upwards inside the tube-type boiler. It exits from the tube-type boiler at the upper end thereof and is distributed again, for instance, by a baffle plate into the wort kettle. Heating operations within a pre-run vessel or in a combined wort kettle and whirlpool tank take place in a similar manner when such an inner boiler is used.
During the heat-up operation in the vessel the wort temperature is not homogeneous. Before the temperature gradient inside the vessel has been substantially compensated for, the inner boiler will overheat its contents, thereby ejecting the contents upwardly at intervals. The wort circuit during the heating operation is thus dicontinuous. It may however happen during this overheating process that deposits are formed on the inner wall of the boiler by the wort because of the low flow rate. This will decrease the service life of the inner boiler and impair the quality of wort.
A circulating circuit has therefore been suggested in patent specification DE 43 04 383 C1 for a wort kettle. The circulating circuit is arranged outside the wort kettle. Wort is laterally withdrawn from the wort kettle and is again introduced from below into the wort kettle underneath the inner tube-type boiler with the aid of a circulating pump. It is in this way that the wort can be force-circulated, and an interval-like ejection and overheating of the wort, specifically during the heating phase, can be avoided.
A large number of technical devices are needed for this external circulating pipe. For instance, an additional pump of adequate capacity, namely a circulating pump, must be provided for.